三峡库区城市富营养化河流凋落物的混合分解效应

Litter mixed decomposition effect of urban eutrophic streams in the Three Gorges Reservoir area

以三峡库区重庆市主城段清水溪为典型的城市富营养化河流代表,选取河岸带3种常见凋落叶为分解对象,设计了7种凋落物组合(3个单种和4个混合物种)和3种孔径的分解袋(50μm、250μm和2mm),开展原位实验,探讨混合凋落物的性状、功能多样性与底栖分解者类群及其交互作用对叶片质量损失和混合效应的影响.结果表明,仅有50%的处理表现为显著非加和效应(且均为负值),这与凋落物的性状密切相关.随着混合凋落物功能离散度的增加,尤其组合中含高木质素等难分解物质的凋落物时,分解变慢.微生物在富营养化河流混合凋落物的分解中占主导作用,小型和大型底栖动物均抑制了混合凋落物的分解过程.在富营养化河流的修复过程中,需重视河流凋落物分解功能,注重调整河岸带植物的配置,以及提升底栖动物的生物多样性并恢复底栖动物在凋落物分解中的正面效应.

The Qingshuixi stream located in Chongqing City of the Three Gorges Reservoir Region was investigated as a typical representative of the urban eutrophication stream.Three common litters in the riparian zone were selected as decomposition objects.The in situ experiment included seven combinations of litters(i.e.,three single treatments and four equal-mass mixed treatments)and three mesh size litter bags(i.e.,50μm,250μm,and 2 mm).The mixed litter traits,functional diversity,decomposer groups,and their interaction on mass loss and mixing effects were explored.Among the above-mentioned mixed treatments,only 50%of the treatments showed significant non-additive effects(and all were negative),which was closely related to the characteristics of litter.As the functional dispersion of mixed litters increased,the decomposition slowed down,especially when litters containing high lignin and other difficult-to-decompose materials are combined.Microbes played a dominant role in the decomposition of mixed litter in the eutrophic streams.In addition,both meiofauna and macrofauna inhibited the decomposition process of mixed litter.These results indicate that in the process of restoration of eutrophic rivers,attention should be paid to the decomposition function of riparian litter.The arrangement of riparian plants should be adjusted and the biodiversity of benthic animals should be improved and then restore the positive effects of benthic animals in litter decomposition.